The increasing concern over joint replacement failure through loosening at the bone-cement interface has prompted evaluation of alternative methods of implant fixation. The concept of using microporous coated implant materials, which allow tissue ingrowth, appears promising as an improved method of fixation. The time period required for fixation through tissue ingrowth may, however, be a limiting factor to clinical application. Studies will be performed to investigate the short-term (0,1,2,3 and 4 weeks) stablilizing ability of low and high modulus microporous systems in weight and non-weight bearing animal environments. Previous long-term animal studies have demonstrated sufficient fixation capability of such systems. However, little work has been done to comparatively evaluate these materials in relation to acrylic bone cement. Using a specially designed implant system this will be accomplished in a canine model over a 25-week interval. In vitro cell culture studies will be performed in an attempt to elucidate initial response to these materials. If it can be shown that adequate implant stabilization is achieved early in the post-operative course, allowing early mobilization, then the use of porous systems may prove to be of significant clinical value.